Direct fired heaters with in-shot burners, tubular combustion chambers, and/or variable venturi

ABSTRACT

Exemplary embodiments of the present disclosure include direct fired heaters and methods relating to the operation of direct fired heaters. An exemplary embodiment of a direct fired heater generally includes one or more in-shot burners and one or more combustion tubes configured to receive combustion air emanating from the one or more in-shot burners. The direct fired heater includes a passageway having an inlet configured to receive or intake a circulating air flow. The passageway may include a venturi portion downstream of the inlet in fluid communication with the exit ends of the combustion tubes. The flow of circulating air through the venturi portion may induce flow of combustion air through the one or more combustion tubes.

FIELD

The present disclosure generally relates to direct fired heaters.

BACKGROUND

This section provides background information related to the presentdisclosure which is not necessarily prior art.

Many gas fired residential furnaces and small commercial heaters (unitheaters under 400,000 BTU per hour (BTU/h)) vent the products ofcombustion to the outdoors. In these types of furnaces and heaters, theproducts of combustion from a burner, such as a ribbon type burner, passthrough a heat exchanger, such as a clamshell-type heat exchanger, andthe flue gasses are routed to the outdoors. Circulating air from withinthe space to be heated is forced over the heat exchangers by acirculating fan, and then distributed throughout the space.

With the requirement for improved efficiency, more recent designs forsmall residential heaters use relatively small diameter tubular heatexchangers in the form of elongated tubes that are generally U-shaped orserpentine shaped. In these designs, the flame is directed into the endof each elongated tube by a burner known as an “in-shot” burner. Smallerdiameter tubes, which have higher restriction to the flow rate of fluegas relative to larger diameter tubes, provide improved heat transfer.But combustion air will not pass through the small diameter tubular heatexchangers by convection alone, and a draft inducer fan is required todraw the combustion air through the heat exchanger tubes and exhaustflue to the outdoors. A circulating blower is still used to forcecirculating air over the heat exchangers, which is then distributedthroughout the space.

Direct fired commercial heaters are usually large, (from 400,000 Btu/hto several million Btu/h), complex, expensive and either of a drawthrough or blow through design. In direct fired commercial heaters,circulation air and products of combustion are vented directly into thespace being heated, unlike indirect fired heaters that vent combustionproducts to the outdoors. Circulating air may be partially or completelydrawn from outside, and circulation air flow to the heater is providedby a circulating air blower. Since all of the heat from combustionremains in the space, efficiency tends to be about 92% for natural gas.(100% less the heat of vaporization of the water in the flue products).The inventor has also recognized that the draw through design is furtherlimited in maximum temperature rise, since the heat from combustionpasses over components, such as the circulating blower motor and throughthe blower itself.

SUMMARY

This section provides a general summary of the disclosure, and is not acomprehensive disclosure of its full scope or all of its features.

Exemplary embodiments of the present disclosure include direct firedheaters and methods relating to the operation of direct fired heaters.An exemplary embodiment of a direct fired heater generally includes oneor more in-shot burners and one or more combustion tubes configured toreceive combustion air emanating from the one or more in-shot burners.The direct fired heater includes a passageway having an inlet configuredto receive or intake a circulating air flow. The passageway may furtherinclude a venturi portion downstream of the inlet in fluid communicationwith the exit ends of the combustion tubes. The flow of circulating airthrough the venturi portion may induce flow of combustion air throughthe one or more combustion tubes.

Another exemplary embodiment of a direct fired heater generally includesa passageway having an inlet configured to intake circulating air and aventuri portion downstream of the inlet. The direct fired heaterincludes baffle movable between at least a first height in which theventuri portion has a first cross-sectional area and a second heightlower than the first height such that the venturi portion has a secondcross-sectional area larger than the first cross-sectional area. Arotating cam device is pivotably coupled to the baffle for pivotalmovement between a first position in which the baffle is at the firstheight and a second position in which the baffle is at the secondheight. An actuator is coupled to the rotating cam device for rotatingthe rotating cam device between the first and second positions toselectively change the height of the baffle between the first and secondheights.

Another exemplary embodiment of a direct fired heater generally includesone or more combustion chambers each having an exit end. The directfired heater includes a circulating air blower configured to establish aflow of circulating air and a passageway. The passageway has an inlet incommunication with the circulating air blower and a venturi portiondownstream of the inlet in fluid communication with the exit ends of theone or more combustion chambers. The passageway is configured such thatcirculating air flow through the venturi portion creates a venturieffect that induces flow of combustion air through the one or morecombustion chambers, without requiring operation of any blower otherthan the circulating air blower.

Another exemplary embodiment of a direct fired heater includes one ormore in-shot burners and one or more combustion tubes configured toreceive combustion air emanating from the corresponding one or morein-shot burners. Each combustion tube has an exit end. A passagewayincludes an inlet configured to intake circulating air and an outletdownstream of the exit ends of the one or more combustion tubes. Thepassageway is configured such that combustion air and circulating airare mixed downstream of the exit ends of the combustion tubes anddischarged from the outlet of the passageway.

An exemplary embodiment of a method relating to the operation of adirect fired heater generally includes inducing combustion air flowthrough one or more combustion chambers by forcing circulating airthrough a venturi portion in fluid communication with the exit ends ofthe one or more combustion chambers.

Another exemplary embodiment of a method relating to the operation of adirect fired heater generally includes operating one or more in-shotburners configured to fire into the one or more combustion tubes havingexit ends. The method may also include mixing combustion air andcirculating air downstream of the exit ends of the one or morecombustion tubes. The method may further include discharging combustionair and circulating air from an outlet of a passageway that isdownstream of the exit ends of the one or more combustion tubes.

Further areas of applicability will become apparent from the descriptionprovided herein. The description and specific examples in this summaryare intended for purposes of illustration only and are not intended tolimit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustrative purposes only ofselected embodiments and not all possible implementations, and are notintended to limit the scope of the present disclosure.

FIG. 1 is a perspective view of a direct fired heater according to anexemplary embodiment;

FIG. 2 is a front view of the direct fired heater shown in FIG. 1;

FIG. 3 is another front view of the direct fired heater shown in FIG. 1with the doors removed so as to illustrate interior areas and componentsof the direct fired heater;

FIG. 4 is another perspective view of the direct fired heater shown inFIG. 1 with portions removed so as to illustrate interior areas andcomponents of the direct fired heater;

FIG. 5 is a perspective view of a portion in FIG. 4 illustrating in-shotburners and tubular combustion chambers or tubes of the direct firedheater shown in FIG. 1 with the burner mounting bracket hidden forclarity;

FIG. 6 is another front view of the direct fired heater shown in FIG. 1with portions removed so as to illustrate interior areas and componentsof the direct fired heater;

FIG. 7 is a view of a portion in FIG. 6 illustrating one embodiment of aventuri portion having an adjustable opening area that may be includedin the direct fired heater shown in FIG. 1;

FIG. 8 is a side view of the direct fired heater shown in FIG. 1 withportions removed so as to illustrate the exit ends of the tubularcombustion chambers or tubes of the direct fired heater;

FIG. 9 is another perspective view of the direct fired heater shown inFIG. 1 with portions removed so as to illustrate interior areas andcomponents of the direct fired heater;

FIG. 10 illustrates an exemplary embodiment of a venturi portion havingan adjustable opening area that may be included in the exemplary directfired heater shown in FIGS. 1 through 9, and illustrating the cam in theup position when there is no power to the actuator and illustrating theheight of the opening in inches for purposes of illustration onlyaccording to exemplary embodiments;

FIG. 11 illustrates the exemplary embodiment shown in FIG. 10 but withthe cam in the down position when the actuator is powered on andillustrating the height of the opening in inches for purposes ofillustration only according to exemplary embodiments; and

FIG. 12 is a line graph illustrating exemplary combustion test resultsmeasured for a prototype of the direct fired heater shown in FIGS. 1through 9 having the dimensions illustrated in FIGS. 10 and 11.

DETAILED DESCRIPTION

Example embodiments will now be described more fully with reference tothe accompanying drawings.

According to one aspect of the present disclosure, there are providedvarious exemplary embodiments of direct fired heaters. An exemplaryembodiment of a direct fired heater generally includes one or morein-shot burners and one or more combustion tubes configured to receivecombustion air emanating from the one or more in-shot burners. The oneor more combustion tubes generally include exit ends through which thecombustion air passes or is discharged. The direct fired heater furtherincludes a passageway having an inlet configured to receive circulatingair flow. The passageway further includes a venturi portion downstreamof the inlet and in fluid communication with, at, or proximate the exitends of the one or more combustion tubes. The passageway and venturiportion are configured such that flow of circulating air through theventuri portion induces or causes flow of combustion air through the oneor more combustion tubes, independent of and/or without requiring theuse of an additional blower (draft inducer fan) specifically provided tocause or induce combustion air flow.

In one or more exemplary embodiments, the passageway may take the formof a plenum having an inlet in communication with a circulating airblower, an outlet through which both the combustion air and circulatingair are discharged, and a venturi-shaped portion downstream of the inletthat defines a constriction between the inlet and the outlet. Theventuri portion forms a constriction or reduced cross-sectional areathrough which circulating air flows, which produces a reduction in fluidpressure downstream of the venturi portion that induces fluid flowthrough the one or more combustion tubes. As disclosed herein, the oneor more combustion tubes may be positioned within the plenum in someembodiments. But in alternative embodiments, one or more combustiontubes may be positioned outside of or external to the plenum, but theexit ends of the one or more combustion tubes may be positioned relativeto (e.g., adjacent, at, etc.) the venturi-shaped portion of the plenumin fluid communication with the venturi-shaped portion.

In various exemplary embodiments, the direct fired heater furtherincludes a circulating air blower for establishing circulating air flow.The circulating air blower forces circulating air through thepassageway, and through the venturi portion, which may be adjacent or atthe exit ends of the tubular combustion chambers or tubes. At theventuri portion, the circulating air flow creates a venturi effect thatinduces the flow of combustion air through the one or more combustiontubes, without requiring the use of any additional blower other than thecirculation air blower. Accordingly, such exemplary embodiments do notrequire any blower that is configured or employed exclusively forestablishing combustion air flow through the combustion tubes, such as adraft inducer fan.

In one or more exemplary embodiments, the direct fired heater mayfurther comprise a venturi portion having an adjustable element, whichis movable for varying the cross-sectional opening area within theventuri portion of the passageway (e.g., plenum, etc.). In suchembodiments, the direct fired heater is configured to control themovement of the adjustable element for varying the fluid pressuredownstream of the venturi portion, which thereby varies the level ofcombustion air flow through the one or more combustion tubes. Thisallows for regulation of the rate of combustion air flow and formaintaining carbon monoxide and/or nitrogen dioxide levels below apredetermined amount to provide for safe operation of the direct firedheater.

In various exemplary embodiments, the direct fired heater may furthercomprise a gas valve in communication with the in-shot burners. The gasvalve may be a valve capable of varying the flow rate of gas to the oneor more in-shot burners. With such gas valves, the direct fired heateris configured to vary the rate of gas flow to the one or more in-shotburners based on a sensed outlet air temperature and temperature risethough the heater, to thereby indirectly sense the outdoor airtemperature and vary the level of heating operation commensurate withthe indirectly sensed outside air temperature.

Exemplary embodiments of the present disclosure include direct firedheaters, such as relatively small direct fired commercial heaters thatmay be 400,000 BTU/h or less. In some embodiments, a direct fired heaterincludes any one of, any combination of, or all of the followingfeatures: in-shot burners, small tubular combustion tubes and/or heatexchangers, venturi-shaped passageways or plenums, and/or venturiportions that are variable, for example, depending on burner inputs. Insome embodiments, a venturi-shaped plenum is used in conjunction with acirculating air blower to create a reduced pressure or “negative”pressure at the exit ends of the combustion tubes for inducing orcausing flow of combustion air through the combustion tubes. This allowsfor the elimination of a draft inducer fan that would provide forcombustion air flow through the combustion tubes.

In various exemplary embodiments, the direct fired heater includes oneor more in-shot burners and one or more corresponding tubular combustionchambers or tubes. The design is modular such that output may beincreased by adding tubes and burners. In this example, all air forcombustion is drawn from outside, and circulating air may be drawn fromoutside or inside. Combustion air and circulating air is mixed andvented directly into the space being heated, unlike indirect firedheaters in which combustion air is vented outdoors. Instead of employinga draft inducer fan to establish combustion air flow through thecombustion tubes, a negative pressure or reduced pressure is generatedby circulating air that is forced through a venturi-shaped plenum, whichcreates a venturi effect at the exit end of the combustion tubes thatinduces flow through the tubes. These features and other aspects of thepresent disclosure will be described in more detail in the followingexemplary embodiments.

With reference now to the figures, FIGS. 1 through 9 illustrate anexemplary embodiment of a direct fired heater 100 embodying one or moreaspects of the present disclosure. In this example of a direct firedheater 100, the combustion air and circulating air may be drawn fromambient air outside of a building or residence. The entire unit may beplaced inside or outside a building. The direct fired heater 100 may berelatively small (e.g., 400,000 Btu/h or less, etc.). Alternativeembodiments may include a larger or smaller direct fired heater that isused for commercial and/or residential purposes.

With continued reference to FIG. 2, the direct fired heater 100 includesa heated air discharge 101, a control panel and/or plenum access door102, and a burner/blower access door 103. A viewport 104 is provided inthe door 103 to allow for viewing of the burner compartment 109. Alsoshown in FIG. 2 are a gas connection 105, electrical connection 106, andan air inlet 107. The heated air discharge 101 and the circulating airintake 107 are also shown in FIG. 6 along with a combustion air intake120.

FIG. 3 illustrates the direct fired heater 100 without the doors 102,103 in order to illustrate the interior areas and components of thedirect fired heater 100. The direct fired heater 100 includes one ormore in-shot burners 108, each in-shot burner having an inlet end 108Aand an outlet end 108B. The in-shot burners 108 are located within theburner compartment 109. The direct fired heater 100 further includes oneor more open-ended combustion tubes 122 (FIG. 6). Each combustion tube122 has an inlet end 121 (FIG. 5) and an exit end 123 (FIG. 7). Theinlet ends 121 of the one or more combustion tubes 122 are configured toreceive combustion air emanating from the corresponding outlet ends 1088of the one or more in-shot burners 108. Thus, in-shot burners 108 areconfigured for firing into the open ended combustion tubes 122 (FIG. 6)(e.g., aluminized steel tubing, etc.). While the tubes 122 are shownwith circular cross-sections in FIG. 8, other embodiments may includeone or more tubes with a non-circular cross section (e.g., rectangular,oval, square, triangular, etc.). In addition, other embodiments mayinclude more or less than the five in-shot burners 108 and more of lessthan five combustion tubes 122 shown in the figures. In one exampleembodiment, the direct fired heater 100 includes five combustion tubeseach of which are 3 feet long with a 2.25 inch diameter, and fivein-shot burners having 0.8 inch diameters and 0.116 inch orifices. Thespecific dimensions in this paragraph (as are all dimensions set forthherein) are provided for purposes of illustration only and not forlimitation, as other embodiments may be configured differently so as toinclude differently configured (e.g., larger or smaller, etc.)combustion chambers and/or burners (e.g., burners of different sizesand/or types besides in-shot burners, etc.).

As shown in FIG. 3, the direct fired heater 100 includes a control panel110. Also shown in FIG. 3, the heater 100 further includes motor andsheave 112, belt 113, and blower and sheave 114, which are part of thecirculating air blower 118 (FIG. 4). The circulating air blower 118 isconfigured to establish the flow of circulating air into the directfired heater 100. The circulating air blower 118 is configured to forcecirculating air through the passageway 111, which is described below.

The passageway 111 has an inlet 111A in communication with thecirculating air blower 118. The passageway 111 further includes aventuri portion 115 that is downstream of the inlet 111A. The venturiportion 115 is in fluid communication with and proximate the exit ends123 (also shown in FIG. 8) of the combustion tubes 122. The passageway111 may further include an outlet 111B through which both combustion airand circulating air are discharged.

While the exemplary direct fired heater 100 is described with referenceto a passageway 111, it should be noted that the passageway 111 may morespecifically comprise a plenum, but may be any shape or constructionsuitable for communication of circulating air therethrough. Thepassageway 111 shown in FIG. 3 may take the form of a plenum having aninlet 111A in communication with a circulating air blower 118, an outlet111B through which both the combustion air and circulating air aredischarged, and a venturi-shaped portion 115 downstream of the inlet111A. The venturi-shaped portion 115 defines a constriction, throat, orreduced cross-sectional area between the inlet 111A and the outlet 111B.Specifically, the cross-sectional area of the opening in the throat orventuri-shaped portion 115 through which circulation air flows issmaller than the cross-sectional area of the inlet opening 111A. Also,the tubes 122 are disposed within the generally box-shaped plenumchamber that tapers or narrows in the direction of air flow through theplenum. In alternative embodiments, however, the combustion tubes 122may be outside of or external to the passageway 111.

The passageway 111, as disclosed herein, may eliminate the need for adraft inducer fan. The passageway 111 and venturi portion 115 areconfigured such that the circulating air flow through the venturiportion 115 creates a venturi effect that induces or causes flow ofcombustion air through the combustion tubes 122, without operation ofany additional blower (draft inducer fan) other than the circulating airblower 118. For this illustrated embodiment, the direct fired heater 100does not require any additional blower that is configured or employedexclusively for establishing combustion air flow through the combustiontubes, such as a draft inducer fan. The venturi portion 115 establishesa constriction or reduced cross-sectional area through which thecirculating air flows, to produce a reduction in fluid pressure at theexit ends 123 of the combustion tubes and downstream of the venturiportion 115. The reduced pressure, which may be called a negativepressure relative to pressure upstream, creates a venturi-effect thatinduces combustion air flow through the one or more combustion tubes.Accordingly, the illustrated direct fired heater 100 does not include adraft inducer fan or induced draft fan.

Also shown in FIG. 4 is a gas valve 117 of the direct fired heater 100,which is in communication with the in-shot burners 108. The gas valve117 supplies a gas, such as natural gas or propane gas, to the in-shotburners 108. The gas is preferably supplied to the in-shot burners 108through a gas manifold 116 that is in communication with the inlet ends108A of the one or more in-shot burners 108.

In one example construction of the exemplary embodiment, the directfired heater 100 may have a venturi portion 115 that includes anadjustable element 127 for varying the cross-sectional area of theopening within the venturi portion 115. The direct fired heater 100 isconfigured to control the movement of the adjustable element 127 tochange the cross-sectional opening area of the constriction provided bythe venturi portion, for varying the fluid pressure downstream of theventuri portion 115. By varying the venturi portion's cross-sectionalopening area, the fluid pressure downstream of the venturi portion 115and venturi effect can be changed, to thereby vary the level ofcombustion air flow through the combustion tubes 122. This allows forregulation of the rate of combustion air flow, and for maintainingcarbon monoxide and/or nitrogen dioxide levels below a predeterminedamount to provide for safe operation of the direct fired heater 100.

In FIG. 7, there shown an exemplary means or assembly by which the fluidpressure at the ends 123 of the tubular combustion chambers or tubing122 may be adjusted, to vary the venturi effect that controls the rateof combustion air flow through the combustion tubes 122. As used herein,the venturi effect generally refers to the reduction in fluid pressurethat results when a fluid flows through a narrower section orconstriction at an increased fluid velocity through the narrower sectionor constriction.

FIG. 7 illustrates an exemplary embodiment of a venturi portion 115having an adjustable opening area that may be included in the directfired heater 100. As shown in FIG. 7, the adjustable venturi portion 115includes an actuator 124 and a rotating cam 125. The actuator 124 maycomprise a two-position actuator having a shaft 126 that is coupled tothe rotating cam 125 for controllably rotating the rotating cam 125between an up or first position (FIGS. 7 and 10) and a down or secondposition (FIG. 11). In this example, the rotating cam 125 may be in theup position (FIGS. 7 and 10) when there is no power to the actuator 124.But the actuator 124 may be powered on to move the rotating cam 125 tothe down or second position (FIG. 11). As can be seen by a comparison ofFIGS. 10 and 11, rotating the cam 125 from the up or first position(FIG. 10) to the down or second position (FIG. 11) changes the height ofthe baffle 127 (e.g., from 3.5 inches to 4 inches in this example,etc.). Thus, the height of the adjustable baffle 127 may be used to varythe cross-sectional opening area of the venturi-shaped portion 115. Whenthe cam 125 is in the up or first position (FIGS. 7 and 10) with nopower to the actuator 124, the cross-sectional opening area or size ofthe venturi portion 115 is smaller than the cross-sectional opening areaor size of the venturi portion 115 when the cam 125 is in down or secondposition (FIG. 11) when the actuator 124 is powered on. The specificdimensions (i.e., 3.5 inches and 4 inches) shown in FIGS. 10 and 11 (asare all dimensions set forth herein) are provided for purposes ofillustration only and not for limitation, as other embodiments may beconfigured differently so as to include a larger or smaller venturiportion.

In some embodiments, an actuator may be provided that is configured tomove the adjustable baffle 127 to one or more positions between thepositions shown in FIGS. 10 and 11. In such embodiments, the height ofthe baffle 127 may be controllably adjusted for infinitely adjusting theventuri effect. Providing an adjustable baffle may provide for betterregulation of combustion, which may depend on burner input or operatinglevel, as will be explained below.

In one or more embodiments, the gas valve 117 of the direct fired heater100 may be a modulating gas valve that is capable of varying the flowrate of gas to the one or more in-shot burners 108. The modulating gasvalve 117 may be configured to adjust the flow rate of gas between afirst, higher flow rate and at least one other reduced flow rate that islower than first, higher flow rate. Alternatively, the gas valve 117 maycomprise a two stage gas valve that is configured to control the flowrate of gas at one of either the first, higher flow rate (which maycomprise a maximum flow rate) or a reduced flow rate. In either case,the direct fired heater 100 may be configured to change the rate of gasflow to the in-shot burners 108 based, at least in part, on outdoor airtemperature. For example, the direct fired heater 100 may be configuredto vary the rate of gas flow to the in-shot burners 108 based on asensed outlet air temperature and temperature rise though the heater, tothereby indirectly sense the outdoor air temperature and vary the levelof heating operation commensurate with the indirectly sensed outside airtemperature.

In a modulating burner where the flow rate of gas is varied, thecombustion air flow within the combustion tubes 122 is affected bychanges in burner fire rate. In the direct fired heater 100, the rate offlow through the combustion tubes 122 may be adjusted as needed tocorrespond to changes in the rate of gas flow to the in-shot burners108, by controlling the actuator 124. The fluid pressure at the ends 123of the combustion tubes 122 may be varied by actuating the rotating cam125 and actuator 126, for example, to adjust the cross-sectional openingarea and resulting venturi effect. In turn, this adjustability may beused, for example, to maintain low carbon monoxide and/or nitrogendioxide levels (e.g., below a predetermined level as shown in FIG. 12,etc.).

In operation, the direct fired heater 100 may include or be incommunication with a temperature sensor for sensing the temperature ofthe outdoor ambient air. As another example, the direct fired heater 100may indirectly sense the temperature of the outdoor or outside ambientair by sensing the outlet air temperature and temperature rise thoughthe heater, and then vary the level of heating operation commensuratewith indirectly sensed outside air temperature.

The direct fired heater 100 may respond to a moderate outside ambienttemperature by controlling the gas valve 117 to establish a reduced gasflow rate (e.g., 50% reduced gas flow rate, etc.). In some embodiments,the gas flow rate may be reduced from an original or initial gas flowrate of 200,000 Btu/hr down to a reduced gas flow rate of 100,000Btu/hr.

Concurrent with the reduced gas flow rate, the direct fired heater 100may be configured to control the actuator 124 to move the adjustablebaffle 127 to the lower height position for increasing (maximizing insome embodiments) the cross-sectional area of the venturi portion 115.The lower height of the baffle 127 reduces the constriction or increasesthe cross-sectional opening area, which in turn reduces the venturieffect and induces a lower rate of flow through the combustion tubes122.

When the outside ambient temperature is cold or low, the direct firedheater 100 may be configured to control the gas valve 117 to establish ahigher gas flow rate (which may be a maximum flow rate in someembodiments). An increase in the rate of combustion without an increasein circulation air flow may lead to undesirable levels of carbonmonoxide and/or nitrogen dioxide. Thus, concurrent with the switch tothe higher gas flow rate (e.g., increasing the gas flow rate from100,000 Btu/hr to 200,000 Btu/hr in some embodiments, etc.), the directfired heater 100 may be configured to control the actuator 124 to movethe adjustable baffle 127 to the second, higher position for reducing(minimizing in some embodiments) the cross-sectional area of the venturiportion 115. The higher height of the baffle 127 increases theconstriction and reduces the fluid pressure, which in turn increases theventuri effect that induces a higher flow rate of combustion air throughthe combustion tubes 122.

FIG. 12 is a line graph illustrating exemplary combustion test resultsin parts per million (ppm) measured for a prototype of the direct firedheater 100 shown in FIGS. 1 through 9 having the dimensions illustratedin FIGS. 10 and 11. For this exemplary testing, the prototype includedfive combustion tubes five combustion tubes each of which are 3 feetlong each with a 2.25 inches in diameter, five in-shot burners having0.8 inch diameters and 0.116 inch orifices, and a one inch top deflectorwithout any nitrogen dioxide baffle. The prototype was configured as a200,000 BTU/h direct fired heater using natural gas and a variablefrequency drive at a frequency of 51.5 Hertz. During this exemplarytesting, the ambient carbon monoxide (CO) was measured to be about 3.62parts per million, the ambient nitric oxide (NO) was measured to beabout 0.0013 parts per million, the ambient nitrogen dioxide (NO₂) wasmeasured to be about 0.0164 parts per million, and the ambienttemperature was measured to be about 51.2 degrees Fahrenheit (° F.). Theshaded area in FIG. 12 indicates CSA allowable combustion, which weresatisfied according to the combustion test results for the prototype ofthe direct fired heater 100. FIG. 12 also shows how the nitrogen dioxideflow rate may be changed by moving the venturi damper position from theup position (FIG. 10) to the down position (FIG. 11), to change thecross-sectional area or size of the venturi portion.

Accordingly, some exemplary embodiments of a direct fired heater may beconfigured such that they are associated with, allow, or provide one ormore of the following features and benefits:

-   -   more heat using less energy with a higher BTU/CFM ratio as        compared to some prior heater designs; and/or    -   certified for both 160° F. temperature rise and 160° F.        discharge temperature at 0° F. outdoor; and/or    -   energy efficient direct gas-fired heating unit; and/or    -   100% combustion efficiency (no flue or heat exchanger losses);        and/or    -   100% non-recirculated fresh air improves indoor air quality;    -   high velocity vertical throw diffuser that reduces        stratification, provides more even heating, and saves energy;        and/or    -   fan only option for summer ventilation; and/or    -   three mounting options (Thru-Wall; Rooftop, Under Roof); and/or    -   LEED (Leadership in Energy and Environmental Design) Ready,        ASHRAE 90.1 compliant design option for LEED/green buildings;        and/or    -   lower installation costs; and/or    -   reduced maintenance costs.

Exemplary embodiments of a direct fired heater (e.g., direct firedheater 100 (FIGS. 1 through 9), etc.) may be sized differently, forexample, according to the heating requirements of the intended end use.By way of example, an exemplary embodiment includes a 200,000 BTU/hdirect fired heater that is about 30⅞ inches tall, about 21¼ incheswide, about 56¼ inches long with a weight of about 300 to about 320pounds. The specific dimensions, numerical values, and materialsidentified in this paragraph (as are all dimensions, numerical values,and materials set forth herein) are provided for purposes ofillustration only and not for limitation, as embodiments disclosedherein may be configured differently to have different configurations(e.g., more than or less than 200,000 BTU/h, etc.).

Exemplary embodiments of a direct fired heater (e.g., 100, etc.) may beused inside or outside of a building. Exemplary embodiments of a directfired heater disclosed herein may be used in warehouses, large storageareas, door/loading dock areas, manufacturing/assembly areas, autorepair/service areas, aircraft hangars/service areas, boat storagebuildings, indoor sports facilities, parking garages, green/LEEDbuildings, etc.

There are also disclosed herein exemplary embodiments of methods, suchas methods relating to the operation of a direct fired heater. Anexemplary embodiment of a method relating to the operation of a directfired heater generally includes inducing combustion air flow through oneor more combustion chambers by forcing circulating air through a venturiportion in fluid communication with the exit ends of the one or morecombustion chambers. Another exemplary embodiment of a method relatingto the operation of a direct fired heater generally includes varying aventuri portion depending on burner input. The venturi portion is influid communication with the exit ends of one or more combustionchambers. Varying the venturi portion adjusts the rate of combustion airflow induced through the one or combustion chambers when circulating airis forced through the venturi portion.

Another exemplary embodiment of a method relating to the operation of adirect fired heater generally includes operating one or more in-shotburners configured to fire into the one or more combustion tubes havingexit ends. The method may also include mixing combustion air andcirculating air downstream of the exit ends of the one or morecombustion tubes. The method may further include discharging combustionair and circulating air from an outlet of a passageway that isdownstream of the exit ends of the one or more combustion tubes.

In a further exemplary embodiment, a method generally includes operatingone or more in-shot burners configured to fire into one or moreopen-ended combustion tubes having exit ends in fluid communication(e.g., proximate, at, etc.) with a venturi portion defining aconstriction. The method may also include operating a circulating airblower to force circulating air through the venturi portion, to create aventuri effect for inducing combustion air flow through the combustiontubes. The method may further include mixing combustion air andcirculating air downstream of the venturi portion and venting combustionair and circulating air into the space being heated. This method (andother methods) may be performed without using a draft inducer fan.Instead, reduced or “negative” pressure in the one or more combustiontubes may be created via a plenum and venturi at the exit ends of thecombustion tubes. This method (and other methods) may include varying oradjusting the cross-sectional opening area of a venturi portion in fluidcommunication with the exit ends of one or more combustion tubes toadjust the venturi effect for better combustion results. This method(and other methods) may include using one or more in-shot burnersconfigured for firing into opened ended combustion tubing (e.g.,aluminized steel tubing, etc.). This method (and other methods) mayinclude increasing heating output capacity of the direct fired heater byadding one or more additional tubular heat exchangers and/or in-shotburners.

Example embodiments are provided so that this disclosure will bethorough, and will fully convey the scope to those who are skilled inthe art. Numerous specific details are set forth such as examples ofspecific components, devices, and methods, to provide a thoroughunderstanding of embodiments of the present disclosure. It will beapparent to those skilled in the art that specific details need not beemployed, that example embodiments may be embodied in many differentforms and that neither should be construed to limit the scope of thedisclosure. In some example embodiments, well-known processes,well-known device structures, and well-known technologies are notdescribed in detail.

The terminology used herein is for the purpose of describing particularexample embodiments only and is not intended to be limiting. As usedherein, the singular forms “a”, “an” and “the” may be intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. The terms “comprises,” “comprising,” “including,” and“having,” are inclusive and therefore specify the presence of statedfeatures, integers, steps, operations, elements, and/or components, butdo not preclude the presence or addition of one or more other features,integers, steps, operations, elements, components, and/or groupsthereof. The method steps, processes, and operations described hereinare not to be construed as necessarily requiring their performance inthe particular order discussed or illustrated, unless specificallyidentified as an order of performance. It is also to be understood thatadditional or alternative steps may be employed.

When an element or layer is referred to as being “on”, “engaged to”,“connected to” or “coupled to” another element or layer, it may bedirectly on, engaged, connected or coupled to the other element orlayer, or intervening elements or layers may be present. In contrast,when an element is referred to as being “directly on,” “directly engagedto”, “directly connected to” or “directly coupled to” another element orlayer, there may be no intervening elements or layers present. Otherwords used to describe the relationship between elements should beinterpreted in a like fashion (e.g., “between” versus “directlybetween,” “adjacent” versus “directly adjacent,” etc.). As used herein,the term “and/or” includes any and all combinations of one or more ofthe associated listed items.

Although the terms first, second, third, etc. may be used herein todescribe various elements, components, regions, layers and/or sections,these elements, components, regions, layers and/or sections should notbe limited by these terms. These terms may be only used to distinguishone element, component, region, layer or section from another region,layer or section. Terms such as “first,” “second,” and other numericalterms when used herein do not imply a sequence or order unless clearlyindicated by the context. Thus, a first element, component, region,layer or section discussed below could be termed a second element,component, region, layer or section without departing from the teachingsof the example embodiments.

Spatially relative terms, such as “inner,” “outer,” “beneath”, “below”,“lower”, “above”, “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. Spatiallyrelative terms may be intended to encompass different orientations ofthe device in use or operation in addition to the orientation depictedin the figures. For example, if the device in the figures is turnedover, elements described as “below” or “beneath” other elements orfeatures would then be oriented “above” the other elements or features.Thus, the example term “below” can encompass both an orientation ofabove and below. The device may be otherwise oriented (rotated 90degrees or at other orientations) and the spatially relative descriptorsused herein interpreted accordingly.

The disclosure herein of particular values and particular ranges ofvalues for given parameters are not exclusive of other values and rangesof values that may be useful in one or more of the examples disclosedherein. Moreover, it is envisioned that any two particular values for aspecific parameter stated herein may define the endpoints of a range ofvalues that may be suitable for the given parameter (i.e., thedisclosure of a first value and a second value for a given parameter canbe interpreted as disclosing that any value between the first and secondvalues could also be employed for the given parameter). Similarly, it isenvisioned that disclosure of two or more ranges of values for aparameter (whether such ranges are nested, overlapping or distinct)subsume all possible combination of ranges for the value that might beclaimed using endpoints of the disclosed ranges.

The foregoing description of the embodiments has been provided forpurposes of illustration and description. It is not intended to beexhaustive or to limit the invention. Individual elements or features ofa particular embodiment are generally not limited to that particularembodiment, but, where applicable, are interchangeable and can be usedin a selected embodiment, even if not specifically shown or described.The same may also be varied in many ways. Such variations are not to beregarded as a departure from the invention, and all such modificationsare intended to be included within the scope of the invention.

1. A direct fired heater comprising: one or more in-shot burners; one ormore combustion tubes configured to receive combustion air emanatingfrom the corresponding one or more in-shot burners, each combustion tubehaving an exit end; and a passageway having an inlet configured tointake circulating air, and a venturi portion downstream of the inlet influid communication with the exits ends of the one or more combustiontubes, the passageway configured such that flow of circulating airthrough the venturi portion induces flow of combustion air through theone or more combustion tubes.
 2. The direct fired heater of claim 1,wherein the passageway is configured such that flow of circulating airthrough the venturi portion induces flow of combustion air through theone or more combustion tubes, without any blower for exclusivelyproviding combustion air flow.
 3. The direct fired heater of claim 1,wherein the passageway further includes an outlet downstream of theventuri portion and the exit ends of the one or more combustion tubes,the outlet operable for discharging combustion air and circulating airout of the direct fired heater.
 4. The direct fired heater of claim 1,wherein the venturi portion defines a constriction having a reducedcross-sectional area that is configured such that air flow through theventuri portion produces a reduction in fluid pressure downstream of theventuri portion, which induces combustion air flow through the one ormore combustion tubes.
 5. The direct fired heater of claim 1, furthercomprising a circulating air blower in communication with the inlet ofthe passageway and operable for forcing circulating air through theventuri portion, to create a venturi effect that induces flow ofcombustion air through the one or more combustion tubes.
 6. The directfired heater of claim 5, wherein the direct fired heater is configuredsuch that combustion air flow is induced through the one or morecombustion tubes without operation of any blower other than thecirculating air blower.
 7. The direct fired heater of claim 1, whereinthe venturi portion includes an element that is movable for varying thecross-sectional opening area of the venturi portion.
 8. The direct firedheater of claim 7, wherein the direct fired heater is configured tocontrol the movement of the element for varying the fluid pressuredownstream of the venturi portion and/or for maintaining carbon monoxideand nitrogen dioxide levels below a predetermined amount.
 9. The directfired heater of claim 1, further comprising a gas valve in communicationwith the one or more in-shot burners and operable for varying the flowrate of gas to the one or more in-shot burners.
 10. The direct firedheater of claim 1, further comprising a baffle movable between at leasta first configuration in which the venturi portion has a firstcross-sectional area and a second configuration in which the venturiportion has a second cross-sectional area larger than the firstcross-sectional area.
 11. The direct fired heater of claim 10, furthercomprising an actuator for moving the baffle between the first andsecond positions.
 12. The direct fired heater of claim 11, wherein theactuator is a two-position actuator that controls the height of thebaffle with a rotating cam device, to move the baffle between the firstand second positions.
 13. The direct fired heater of claim 10, whereinthe direct fired heater is configured to control the movement of theadjustable baffle for varying the fluid pressure downstream of theventuri portion, to thereby allow for regulation of the level ofcombustion air flow through the one or more combustion tubes to maintaincarbon monoxide and/or nitrogen dioxide below a predetermined amount.14. The direct fired heater of claim 10, further comprising a gas valvein communication with the one or more in-shot burners, and configured tovary the rate of gas flow between a first gas flow rate and at least onereduced gas flow rate, wherein the direct fired heater is configured tocontrol the gas valve to establish the first gas flow rate when thebaffle is in first configuration and to establish the at least onereduced gas flow rate when the baffle is in the second configuration.15. The direct fired heater of claim 1, wherein the passageway comprisesa plenum.
 16. A direct fired heater comprising: one or more combustionchambers each having an exit end; a circulating air blower configured toestablish a flow of circulating air; and a passageway having an inlet incommunication with the circulating air blower, a venturi portiondownstream of the inlet in fluid communication with the exit ends of theone or more combustion chambers, the passageway configured such thatcirculating air flow through the venturi portion creates a venturieffect that induces flow of combustion air through the one or morecombustion chambers, without requiring operation of any blower otherthan the circulating air blower.
 17. The direct fired heater of claim16, further comprising an adjustable element for varying thecross-sectional opening area of the venturi portion.
 18. The directfired heater of claim 16, further comprising a baffle movable between atleast a first configuration in which the venturi portion has a firstcross-sectional area and a second configuration in which the venturiportion has a second cross-sectional area larger than the firstcross-sectional area.
 19. The direct fired heater of claim 16, furthercomprising one or more in-shot burners configured such that the one ormore combustion chambers receive combustion air emanating from thecorresponding one or more in-shot burners.
 20. The direct fired heaterof claim 16, wherein the one or more combustion chambers comprise tubes.21. The direct fired heater of claim 16, wherein the passagewaycomprises a plenum and an outlet through which combustion air andcirculating air are discharged.
 22. A direct fired heater comprising: apassageway having an inlet configured to intake circulating air and aventuri portion downstream of the inlet; a baffle movable between atleast a first height in which the venturi portion has a firstcross-sectional area and a second height lower than the first heightsuch that the venturi portion has a second cross-sectional area largerthan the first cross-sectional area; a rotating cam device pivotablycoupled to the baffle for pivotal movement between a first position inwhich the baffle is at the first height and a second position in whichthe baffle is at the second height; and an actuator coupled to therotating cam device for rotating the rotating cam device between thefirst and second positions to selectively change the height of thebaffle between the first and second heights.
 23. The direct fired heaterof claim 22, wherein the direct fired heater includes: one or morein-shot burners, each in-shot burner having an inlet end and an outletend; one or more combustion tubes, each combustion tube having an inletend and an exit end, the inlet ends of the one or more combustion tubesbeing configured to receive combustion air emanating from thecorresponding outlet ends of the one or more in-shot burners, the exitends in fluid communication with the venturi portion such thatcirculating air flow through the venturi portion creates a venturieffect that induces flow of combustion air through the one or morecombustion tubes.
 24. The direct fired heater of claim 23, wherein thedirect fired heater includes a circulating air blower in communicationwith the inlet of the passageway and operable for forcing circulatingair through the venturi portion, to create a venturi effect that inducesflow of combustion air through the one or more combustion tubes, withoutrequiring the use of an additional blower specifically provided toinduce combustion air flow.
 25. The direct fired heater of claim 22,wherein the direct fired heater is configured such the height of thebaffle between the first and second height is varied based on burnerinput.
 26. A direct fired heater comprising: one or more in-shotburners; one or more combustion tubes configured to receive combustionair emanating from the corresponding one or more in-shot burners, eachcombustion tube having an exit end; and a passageway having an inletconfigured to intake circulating air and an outlet downstream of theexit ends of the one or more combustion tubes, the passageway configuredsuch that combustion air and circulating air are mixed downstream of theexit ends of the combustion tubes and discharged from the outlet of thepassageway.
 27. The direct fired heater of claim 26, wherein thepassageway includes a venturi portion downstream of the inlet in fluidcommunication with the exit ends of the one or more combustion chambers,the passageway configured such that circulating air flow through theventuri portion creates a venturi effect that induces flow of combustionair through the one or more combustion chambers.
 28. The direct firedheater of claim 26, wherein the direct fired heater includes acirculating air blower in communication with the inlet of the passagewayand operable for forcing circulating air through the passageway toinduce flow of combustion air through the one or more combustion tubes,without requiring the use of an additional blower specifically providedto induce combustion air flow.
 29. The direct fired heater of claim 26,further comprising an adjustable element for varying the cross-sectionalopening area of a portion of the passageway.
 30. The direct fired heaterof claim 26, further comprising a baffle movable between at least afirst configuration in which a portion of the passageway has a firstcross-sectional area and a second configuration in which the portion ofthe passageway has a second cross-sectional area larger than the firstcross-sectional area.
 31. The direct fired heater of claim 26, whereinthe passageway comprises a plenum.
 32. The direct fired heater of claim26, further comprising: a baffle movable between at least a first heightin which a portion of the passageway has a first cross-sectional areaand a second height lower than the first height such that the portion ofthe passageway has a second cross-sectional area larger than the firstcross-sectional area; a rotating cam device pivotably coupled to thebaffle for pivotal movement between a first position in which the baffleis at the first height and a second position in which the baffle is atthe second height; and an actuator coupled to the rotating cam devicefor rotating the rotating cam device between the first and secondpositions to selectively change the height of the baffle between thefirst and second heights.
 33. A method relating to operation of a directfired heater, the method comprising inducing combustion air flow throughone or more combustion chambers by forcing circulating air through aventuri portion in fluid communication with the exit ends of the one ormore combustion chambers.
 34. The method of claim 33, further comprisingvarying the venturi portion to adjust the rate of combustion air flowinduced through the one or combustion chambers when circulating air isforced through the venturi portion.
 35. The method of claim 33, furthercomprising varying the cross-sectional opening area of the venturiportion.
 36. The method of claim 33, wherein the method includesoperating a circulating air blower to force circulating air through theventuri portion.
 37. The method of claim 33, wherein the direct firedheater does not include a draft inducer fan, and wherein the methodincludes operating a circulating air blower to force circulating airthrough the venturi portion to create a venturi effect for inducingcombustion air flow through one or more combustion chambers.
 38. Amethod relating to operation of a direct fired heater, the methodcomprising: operating one or more in-shot burners configured to fireinto the one or more combustion tubes having exit ends; mixingcombustion air and circulating air downstream of the exit ends of theone or more combustion tubes; and discharging combustion air andcirculating air from an outlet of a passageway that is downstream of theexit ends of the one or more combustion tubes.
 39. The method of claim38, further comprising inducing combustion air flow through the one ormore combustion chambers by forcing circulating air through a venturiportion of the passageway that is in fluid communication with the exitends of the one or more combustion chambers.